I can't believe this , what a disappointment as Lumia 830 has sen-score technology build-in. found this tread just confirms what you guys are saying
"The Lumia Denim operating system update also brings a "Hey Cortana" voice command to activate the search assistant hands-free. On this Lumia 830, however, we couldn't get this to work as apparently it's only functional with phones that have Qualcomm Snapdragon 800 and above processors - but Microsoft won't confirm this yet. Instead a press-and-hold the search icon get the voice assistant to pay attention. "
I am going to contract Microsoft today via chat online to confirm will let you all know thanks for the reply back.